Monolithic ceramic tubes are often used in heat exchanger applications. They are used in high temperature environments and have a relatively low purchase price. In some cases the tribological properties of ceramic material are important. For example, ceramic tube heat exchangers are useful as part of coal fired regenerative heat exchangers used to supply gas turbines with high temperature (e.g., 1200.degree. F. to 2000.degree. F.), high pressure (e.g., 200 psi) air.
While monolithic ceramic tubes may have low initial cost, the cost effectiveness of the tubes is often not acceptable. Original flaws in the ceramic tube and flaws developed during use or by damage from external sources often culminate in catastrophic failure of the tube. That is, the flawed tube, due to the high internal pressure to which it is often subjected, blows up or explodes when it fails. In many applications, multiple tubes are in close proximity to each other and therefore, in the event of failure of one tube, the pieces of the broken tube become projectiles and destroy adjacent tubes. This creates a cascading effect and ultimately results in the destruction of many or all of the tubes in a heat exchanger. This type of failure, with pieces of broken tubes flying about, is especially destructive when the heat exchanger is used at the hot air intake of a gas turbine.
One way to get around the breakage problems of ceramic tubes is to use metal tubes instead of ceramic tubes. Two primary disadvantages of metal tubes are their temperature limitations and their corrosion limitations. In addition to the temperature and corrosion limitations, metal tubes are usually quite heavy and often suffer from fatigue failure. Metals which are more resistant to high temperatures and corrosion are very often too expensive to use.